350 m Observations of Asteroids, Secondary Calibrators, and Stellar Standard(s)
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350 m Observations of Asteroids, Secondary Calibrators,
and Stellar Standard(s)
C. Darren DowellJet Propulsion Laboratory,
California Institute of Technology,USA
2008 Feb 7
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Scope of this Project• CSO/SHARC II 350 m archive (2003-date):
– bright (>2 Jy), compact calibrators for ground-based use; 10% accuracy goal
– limited observations of fainter calibrators for Herschel• Calibration relative to Mars, Uranus, Neptune
– Starlink FLUXES program from JCMT:• Mars: TB ≈ 210 K (Wright 1976; Wright 1995, priv. commun.)• Uranus: TB = 64.0 K (Griffin & Orton 1993)• Neptune: TB = 60.9 K (1% below Griffin & Orton 1993)
• Paper (Dowell, Sandell, et al.) to be produced this year.– Analysis shown today is preliminary.– 10% uncertainty unless stated otherwise.
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SHARC II/CSO
• eff = 350 m• main beam: 8.5˝ FWHM
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Data Analysis
• Nonlinearity correction (≤ 25%)• Calibration of atmospheric absorption
based on total power on bolometer array
• 28’’ aperture for photometry• simultaneous fit over all sources, using
Mars, Uranus, Neptune as fixed references
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Bright Secondary Standards
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Bright Secondary Standards
star fo
rmation sit
es
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Bright Secondary Standards
evolved sta
rs
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Evolved Stars
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Evolved Stars
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Evolved StarsF = 23.3 Jy ± 16%, T = 593 d
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Evolved StarsF = 23.3 Jy ± 16%, T = 593 d
IRC+10216: 32.4 Jy ± 13%, T = 671 d
Cet: 2.30 Jy ± 29%, T = 330 d
CIT6: 3.02 Jy ± 11%, T = 572 d
CRL618: no sign of variability
CRL2688: no sign of variability
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Miscellaneous 350 m Point Sources
• Galilean Satellites:– Callisto: TB = 128 K (within 5% of de Pater et al. 1989)– Ganymede: TB = 117 K (within 3% of de Pater et al. 1989)
• Stellar Disks:– HL Tau: 17.0 Jy– TW Hya: 6.48 Jy– Oph SR 21A: 3.79 Jy– limited data on numerous ~1 Jy disks
• Extragalactic:– Arp 220: 11.4 Jy– Mrk 231: 1.92 Jy ± 15%– limited data on numerous ~1 Jy IR galaxies
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Mars, Uranus, Neptune
• Mars vs. Uranus:– 2005 May 13, 15.2-16.5 UT, stable conditions
• observed Mars/Uranus = 18.5, 7±2% lower than FLUXES prediction
– However, for full archive, observed Mars/Uranus is low by only 3%.
• Mars vs. Neptune:– Over full archive, Mars/Neptune is low by 7%.
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Asteroids
• Simple model:– TB = T1AU (r / 1 AU)-1/2
• r = heliocentric distance
– F = B(TB)
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Bright, Well-Observed AsteroidsT1AU = 292 K
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Bright, Well-Observed Asteroids
r.m.s. of residuals: 7%
T1AU = 292 K
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Bright, Well-Observed Asteroids
r.m.s. of residuals: 7%
Pallas: T1AU = 326 K; r.m.s.: 7%
Vesta: T1AU = 248 K; r.m.s.: 11%
T1AU = 292 K
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Pallas: TB vs. heliocentric distance
TB = T1AU (r / 1 AU)-1/2
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Asteroids at 350 m (10-25% unc.)• Hygiea (C): T1AU = 412 K• Metis (S): 339 K• Juno (S): 334 K• Pallas (B): 326 K• Davida (C): 292 K• Ceres (C): 292 K• Egeria (G): 289 K• Vesta (V): 248 K• Psyche (M): 200 K
• also observations of: Amphitrite (S), Cybele (C), Diotima (C), Europa (C), Io (C)
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Stellar Standard Boo
• F = 0.54 Jy• within 20% of
model prediction (W. Vacca, priv. commun.)
• only IR stellar standard detected so far at 350 m
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What is needed now for ground-based observations in support of Herschel?
• CSO will continue observations of bright calibrators.• Difficult to get observing time for faint Herschel
calibrators.– If important, consider buying CSO time?
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• This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA).